Armed men take up positions Saturday outside the Parliament building in Simferopol, in the Crimea region of Ukraine. Russian President Vladimir Putin asked the Russian Senate to send troops to Ukraine, a strong response to U.S. President Barack Obama's warning just hours earlier that Russia should respect Ukraine's sovereignty.

FILE -- Russian President Vladimir Putin, right, with Ukranian President Viktor Yanukovych during a press conference at the Grand Kremlin Palace in Moscow, Dec. 17, 2013. Local reports suggest that Putin is protecting Ukraine's deposed president and the Russian Parliament has granted Putin the authority he sought to use military force in response to the deepening instability in Ukraine, a strong response to U.S. President Barack Obama's warning that Russia should respect Ukraine's sovereignty. (Mikhail Klimentiev/Pool via The New York Times) -- EDITORIAL USE ONLY.

Feb. 23: Parliament gives interim presidential authority to the speaker, Oleksandr Turchynov, a leader of the opposition. In Crimea, pro-Russian protesters rally against the new government.

Monday: An arrest warrant is issued for Yanukovych for his role in the deaths of dozens of protesters killed by riot police.

Tuesday: A Russian flag is raised on a major government building. Crowds scuffle in Kharkiv, a large city in eastern Ukraine.

Wednesday: Moscow orders what it says are routine military exercises in a district bordering Ukraine and puts troops in the region on high alert. U.S. Secretary of State John Kerry says any Russian military intervention would be a “grave mistake.”

Thursday: Pro-Russia gunmen take over the regional parliament building in Crimea. Yanukovych, who hadn’t been heard from in days, resurfaces in Russia.

Friday: Heightened Russian military activity in Crimea prompts a warning from President Barack Obama, who says there “will be costs for any military intervention.” The new Ukrainian government says hundreds of soldiers in green camouflage, but without insignia, have taken over two airports in Crimea.

Saturday: Russia’s lower house of parliament grants Putin permission to send troops to Ukraine. Crimea’s pro-Russian leader claims control of the military and police in the region.

— The Washington Post

SIMFEROPOL, Ukraine — Russian armed forces seized control of Ukraine’s Crimean Peninsula on Saturday, as the Russian Parliament granted President Vladimir Putin broad authority to use military force in response to the political upheaval in Ukraine that dislodged a Kremlin ally and installed a new, staunchly pro-Western government.

Russian troops stripped of identifying insignia but using military vehicles bearing the license plates of Russia’s Black Sea force swarmed the major thoroughfares of Crimea, encircled government buildings, closed the main airport and seized communication hubs, solidifying what began Friday as a covert effort to control the largely pro-Russian region.

In Moscow, Putin convened the upper house of Parliament to grant him authority to use force to protect Russian citizens and soldiers not only in Crimea but throughout Ukraine. Both actions — military and parliamentary — were a direct rebuff to President Barack Obama, who on Friday pointedly warned Russia to respect Ukraine’s territorial integrity.

Obama accused Russia on Saturday of a “breach of international law” and condemned the country’s military intervention, calling it a “clear violation” of Ukrainian sovereignty.

In Crimea, scores of heavily armed soldiers fanned out across the center of the regional capital, Simferopol. They wore green camouflage uniforms with no identifying marks, but spoke Russian and were clearly part of a Russian mobilization.

Large pro-Russia crowds rallied in the eastern Ukrainian cities of Donetsk and Kharkiv, where there were reports of violence. In Kiev, the Ukrainian capital, fears grew within the new provisional government that separatist upheaval would fracture the country just days after a winter of civil unrest had ended with the ouster of President Viktor Yanukovych, the Kremlin ally who fled to Russia.

In addition to the risk of open war, it was a day of frayed nerves and set-piece political appeals that recalled ethnic conflicts of past decades in the former Soviet bloc, from the Balkans to the Caucasus.

Obama, who had warned Russia on Friday that “there will be costs” if it violated Ukraine’s sovereignty, spoke with Putin for 90 minutes Saturday, according to the White House, and urged him to withdraw his forces back to their bases in Crimea and to stop “any interference” in other parts of Ukraine.

In a statement afterward, the White House said the United States would suspend participation in preparatory meetings for the G8 economic conference to be held in Sochi, Russia, in June and warned of “greater political and economic isolation” for Russia.

The Kremlin offered its own description of the call, in which it said Putin spoke of “a real threat to the lives and health of Russian citizens” in Ukraine and warned that “in case of any further spread of violence to Eastern Ukraine and Crimea, Russia retains the right to protect its interests and the Russian-speaking population of those areas.”

In Britain, Prime Minister David Cameron said “there can be no excuse for outside military intervention” in Ukraine.

Canada said it was recalling its ambassador from Moscow and, like the United States, suspending preparations for the G8 meeting. At the United Nations, the Security Council held an emergency meeting on Ukraine for the second time in two days. The U.S. ambassador, Samantha Power, called for an international observer mission, urged Russia to “stand down” and took a dig at the Russian ambassador, Vitaly Churkin, on the issue of state sovereignty, which the Kremlin frequently invokes in criticizing the West over its handling of Syria and other disputes.

“Russian actions in Ukraine are violating the sovereignty of Ukraine and pose a threat to peace and security,” she said.

Yanukovych’s refusal, under Russian pressure, to sign new political and free trade agreements with the European Union last fall set off the civil unrest that last month led to the deaths of more than 80 people, and ultimately unraveled his presidency. The country’s new interim government has said it will revive those accords.

Ukraine’s acting president, Oleksandr Turchynov, said at a briefing in Kiev on Saturday evening that he had ordered Ukraine’s armed forces “to full combat readiness.” A Ukrainian military official in Crimea said Ukrainian soldiers had been told to “open fire” if they came under attack by Russian troops or others, though it was unlikely they could pose a serious challenge to Russian forces.

Officials in Kiev demanded that Russia pull back its forces, and confine them to the military installations in Crimea that Russia has long leased from Ukraine.

The fast-moving events began in the morning, when the pro-Russia prime minister of Crimea, Sergei Aksyonov, declared that he had sole control over the military and the police, and appealed to Putin for Russian help in safeguarding the region. He also said a public referendum on independence would be held March 30.

The Kremlin quickly issued a statement saying that Aksyonov’s plea “would not be ignored,” and within hours the upper chamber of Russia’s Parliament had authorized military action.

The authorization cited Crimea, where Russia maintains important military installations, but covered the use of Russian forces in the entire “territory of Ukraine.” Parliament also asked Putin to withdraw Russia’s ambassador to the United States.

As soldiers mobilized across the peninsula, the region’s two main airports were closed, with civilian flights canceled, and they were guarded by heavily armed men in military uniforms.

Similar forces surrounded the regional Parliament building and the rest of the government complex in downtown Simferopol, as well as numerous other strategic locations, including communication hubs and a main bus station.